The Apnea Risk Evaluation System (ARES) is an inexpensive, in-home method assessing for sleep-disordered breathing. ARES utilizes expert software to integrate analysis of nocturnal oxygen saturation, pulse rate, snoring sounds, head position/movement recordings acquired with a self-applied, portable single-site (forehead) device with analysis of responses to a clinical questionnaire. During Phase II, an ARES reflectance sensor will be developed to optimize results obtained from in-home recordings and to reduce cost and between-unit variability. The ARES pulse oximeter will be compared to commercial oximeters and co-oximetry during normoxic and hypoxic steady state conditions and during breath-holds at functional residual capacity. Additional algorithms will be implemented to assist in the characterization of abnormal respiratory events and to identify probable arousals. To broaden clinical acceptance, the off-line analysis software will be expanded to allow researchers and sleep medicine professionals to visually inspect the automated ARES algorithm results and modify the scoring.